Tires are subjected to one of the harshest environments experienced by any consumer product. In addition to being stretched millions of times as they roll through their life, tires are exposed to acid rain, brake dust, harsh chemicals and direct sunlight, as well as summer's heat and winter's cold. In some cases, tires may develop cracks in the tire rubber in these environments.
Poor tire maintenance practices (or other conditions) can increase the likelihood of developing cracks. For example, driving on a tire that is flat or a run flat tire under run flat conditions, or one that is underinflated or overloaded causes excessive stretching of the rubber compound, and may result in (or exacerbate) cracks.
In addition, simple exposure of tires to the elements can eventually cause rubber to lose some of its elasticity and allow surface cracking to appear. These cracks typically develop in the sidewalls or at the base of the tread grooves. Cracking can be accelerated by too much exposure to heat, vehicle exhaust, ozone and sunlight. Additionally, some sidewall cracking has been linked to abrasion from parking against a curb, or the excessive use of tire cleaners/dressings that inadvertently remove some of the tire's anti-oxidants and anti-ozonants protection during every cleaning procedure. Depending on their severity, they may be cosmetic in nature if they don't extend past the rubber's outer surface, or may be a reason to replace the tire if they reach deep into the rubber.
The repeated stretching of the rubber compound actually helps resist cracks forming. The tires used on vehicles that are driven infrequently, or accumulate low annual mileage are more likely to experience cracking because long periods of parking or storage interrupt “working” the rubber. In addition to being an annoyance to show car owners, this condition often frustrates motor home and recreational vehicle owners who only take occasional trips and cannot park their vehicle in a garage or shaded area. Using tire covers at least minimizes direct exposure to sunlight.
It would thus be desirable to provide a tire with an ability to repair its own cracks by repairing damage to the polymeric structure of the tire, thereby maintaining strength and durability, and extending the life of the tire.